Planet layers:
https://www.solarsystemscope.com/textures/download/8k_venus_surface.jpg
https://www.solarsystemscope.com/textures/download/4k_eris_fictional.jpg

Asteroids:
https://img.freepik.com/free-photo/black-white-details-moon-texture-concept_23-2149535760.jpg?w=2000
https://img.freepik.com/free-photo/black-white-details-moon-texture-concept_23-2149535764.jpg?w=2000
https://static9.depositphotos.com/1011845/1198/i/600/depositphotos_11983420-stock-photo-moon-ground-semalss-texture.jpg
https://www.reddit.com/r/Unity3D/comments/6sdq7s/i_just_made_a_seamless_lunar_surface_texture_you/
https://i.imgur.com/NPJfZXGl.png
https://i.pinimg.com/originals/19/33/0b/19330beb4d18d4baf9a522a3649210a5.jpg
https://as2.ftcdn.net/v2/jpg/00/50/64/23/1000_F_50642395_EzECINojo0khiXKgl33LOnoNwNBIhSNm.jpg
https://filterforge.com/filters/13302.jpg
https://filterforge.com/filters/13302-v1.jpg
https://filterforge.com/filters/1134.jpg
https://filterforge.com/filters/214.jpg
https://filterforge.com/filters/1306.jpg
https://www.deviantart.com/hhh316/art/Seamless-Fire-Texture-333891187

Black tripanels: (not used)
https://www.amazon.co.uk/Homelet-Adhesive-Panelling-Cladding-Textured/dp/B09GF6X5V9

UFO:
https://www.turbosquid.com/3d-models/sci-fi-ufo-2-3d-model/1062607#